Wood Science and Technology

, Volume 51, Issue 4, pp 855–872 | Cite as

Hydroalcoholic extracts from the bark of Quercus suber L. (Cork): optimization of extraction conditions, chemical composition and antioxidant potential

  • Ivo M. ArosoEmail author
  • Ana R. Araújo
  • João P. Fernandes
  • Tânia Santos
  • Maria T. Batista
  • Ricardo A. Pires
  • João F. Mano
  • Rui L. Reis


Cork is the bark of the tree Quercus suber L. which finds use in diverse applications. However, a significant percentage is still rejected and burned for energy production, despite containing valuable molecules for materials processing and with important biological activities. Herein, the optimization of the extraction process to obtain these molecules, using mild solvents and conditions, is described within a biorefinery perspective. The extracts were obtained by direct contact solvent extractions with water, ethanol and its mixtures for different time and temperatures, and evaluated for chemical composition, total phenolic content (TPC) and antioxidant properties [by DPPH radical scavenging, ferric reducing antioxidant power (FRAP), Trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assays]. The results showed that the extraction process is accelerated and higher yields are achieved with the increase in temperature without chemical degradation or compromising the antioxidant capacity. For all solvents, at reflux temperature, more than 90% of the extractable material is obtained within 6 h (80% within 1 h). The highest TPC and antioxidant capacity are observed for the extracts obtained with mixtures of water and ethanol of similar volumes. The antioxidant capacity measured by DPPH, FRAP and TEAC assays was found to be proportional to the extract TPC, while ORAC is favored for higher percentages of ethanol on the extracting solvent. The main constituents of these extracts are the ellagitannins, vescalagin, castalagin and β-O-ethylvescalagin, along with other phenolic acids (mainly ellagic and gallic acids) and various flavonols. The extracts stability was monitored up to 1 year of storage with neither reduction in the antioxidant capacity nor chemical degradation. These results show that extracts with strong antioxidant potential and high content of bioactive molecules can be obtained from the processing of waste streams. Cork is a sustainable forest product and the development of new fields of application contributes toward a zero waste cycle for a complete material biorefinery.


DPPH Total Phenolic Content Ellagic Acid Trolox Equivalent Antioxidant Capacity Ferric Reduce Antioxidant Power 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



The authors are grateful to Amorim Cork Composites for providing the cork powder and for the financing provided by the COMPETE/QREN/EU funding program through project BioActiveCork (QREN FCOMP-01-0202-FEDER-005455). Ivo M. Aroso and João P. Fernandes acknowledge the financial support from FCT through grants SFRH/BD/42273/2007 and SFRH/BD/73162/2010, respectively. Funding was also granted from the European Union’s Seventh Framework Programme (FP7/2007–2013) under Grant Agreement No. REGPOT-CT2012-316331-POLARIS and from Project “Novel smart and biomimetic materials for innovative regenerative medicine approaches (Ref.: RL1 - ABMR - NORTE-01-0124-FEDER-000016)” co-financed by North Portugal Regional Operational Programme (ON.2 – O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF). Conflict of Interest: The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2017

Authors and Affiliations

  1. 1.3B’s Research Group - Biomaterials, Biodegradables and Biomimetics, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative MedicineUniversity of MinhoBarco GMRPortugal
  2. 2.ICVS/3B’s - PT Government Associate LaboratoryBraga, GuimarãesPortugal
  3. 3.Center for Neuroscience and Cell BiologyUniversity of CoimbraCoimbraPortugal
  4. 4.Center for Pharmaceutical Studies - Faculty of PharmacyUniversity of CoimbraCoimbraPortugal

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